Electric cut-out.



G. WRIGHT.

ELECTRIC CUT-OUT..

APPLICATION FILED MAY 5.1915.

1,265,576. Patented May 7, 1918.v

/ Inventor:

Gilbert Wright,

His JIttorneg.

UNITED sTA ns PATENT OFFICE.

GILBERT WRIGHT, OF SCHENECTAD Y, NEW YORK, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

ELECTRIC CUT-OUT.

Specification of Letters Patent.

Patented May '7, 1918.

Application filed May 5, 1915. Serial No. 25,908.

To all whom it may concern:

Be it known that I, GILBERT WRIGHT, a citizen of the United States, residing at Schenectady, in the county of Schenectady, State of New York, have invented certain new and useful Improvements in Electric Gut-Outs, of which the following is a specification.

My invention relates to electric cut-outs in which opening of a circuit under conditions of excessive current flow is brought about by overheating of a fusible member or body in consequence of such flow. Among the advantages obtainable in connection with my invention I may mention simplicity and ruggedness of construction, ease and cheapness in manufacture, practical eifectiveness, and convenience in use in the replacement of parts liable to destruction or deterioration. Cut-outs constructed in accordance with my invention are especially suitable for motors and other apparatus whose capacity for enduring overloads and other conditions of excessive current flow without injury depends on the duration of the abnormal current as well as on itsabsolute magnitude. The invention itself comprises various novel features and details and combinations and arrangements of parts best set forth by the description of particular devices embodying them, .its scope being as indicated in my claims.

In the accompanying drawing, Figure 1 is a mid-sectional view of a cut-out constructed in accordance with my invention.

Fig. 2 is an enlarged detail view of the fusible member shown in Fig. 1 as seen from above; and Fig. 3 is a similar view of a somewhat diiferent form of fusible member.

Fig. 4: is a fragmentary side view of a contact member in the nosltion indicated in dotted lines in Fig. 1.

Fig. 5 is a bottom view of the device, parts below the line 55 in Fig. 1 being broken away and removed.

Fig. 6 is a fragmentary exterior side view of the upper end of the device vwith the cover removed.

Fig. 7 is a diagrammatic view illustrating the use of the device with an electric motor.

As shown in Fig. 1, the cut-out comprises .a relatively rigid brass contact member or post 1 and a springy, resilient contact member 2. The spring contact member 2 is of laminated member 2 is fixed at one end, and it is ordinarily bent toward the member 1 and held thus flexed by means of the fuse member 5, which is shown as a closed metal linkhaving the general form of the letter U. This member 5, it will be seen, is slipped over the ends of the post member 1 and the spring member 2 serves to maintain them in electrical connection, even though, as shown, they be not held in actual contact with one another. As will be seen from Figs. 1 and 2, the link member 5 is readily fusible at the sides of the U, since it consists of a U-shaped yoke piece of brass or copper and a brass'or copper bar secured against the ends of the U across its opening by means of readily fusible solder or other alloy. The U-shaped link member 55 shown in Fig. 3 is also readily fusible at the sides of the U, being made wholly of solder or other readily fusible metal. Under conditions of excessive current flow, the spring contact member 2 is released and its electrical connection with the member 1 broken by fusion at the sides of the link member 5 or 55.

The heat necessary for the release of the spring member 2 is developed by heater means 7 associated with the member 1, and is transmitted to the link member 5 by conduction through said member 1. The heater 7, it will be seen, comprises enameled or otherwise electrically insulated resistance wire 8 compactly coiled on the member 1.

The coil of wire 8 is embedded in cement 9 of low thermal conductivity, and this, in turn, is enveloped in a paper jacket. As shown, one end of the wire 8 is soldered in a hole in the member 1, and its other end is so connected that the wire forms the current connection for said member 1 and is traversed by the entire current passing between the members 1 and 2. This latter connection will presently be described, as gvell as the connection of the spring mem- Referring once more to Fig. 1, it will be seen that for mounting the operating parts thus far described there is provided a base or insulating support '10. The device being intended for use in sockets of the Edison screw type, the base 10 is provided with an encircling screw shell terminal 11 and with center terminal means 12. As shown, the base 10 comprises two separate parts 13 and 14 of porcelain, bisque, or other insulating material; the screw shell 11 is around the part 13 and has a flange or mutilated bottom portion extending between the parts 13 and 14; and the center contact means 12 is in the form of a hollow rivet that serves to. secure the parts 13 and 14 together and clamp the aforesaid flange between them. It will further be seen that the adjacent faces of the parts 13 and 14 have respectively a shallow circular depression or seat and a slight corresponding bevel edged projection, and that the bottom portion of the shell 1.1 is turned upward on a bevel so as to cooperate with said seat and projection in centering and holding the shell.

The insulating part 13 has a recess or socket that receives the tapering frustopyramidal lower end of the contact member or part 1, which is secured therein by a screw 15 extending out through the side of the socket, its head bein shrouded in a recess at one side of sai part 13, but still conveniently accessible. The lower end of the heater Wire 8 extends down through a ,hole in-the part 10 and is soldered in the center terminal 12 at 16. The spring contact member 2 extends down to the screw shell 11 through a hole 17 in the part 10, and its lower end 18 is bent so as to lie between the flange portion of said shell 11 and said part 13 with the copper strip 4 against the shell flange. The bent-over end 18 of the copper strip 4 may be merely clamped tight between the parts 11 and 13; or it may be welded, soldered, brazed, or otherwise fastened to said part 11 for the sake of a better electrical connection. For mechanical reasons, it may even be found advantageous to fasten the ends of the strips 3 and 4 to one another at 18. As shown in Fig. 4, the upper end of the copper strip 4 is secured to that of the spring strip 3 by being bent over on it. It may alternatively or in addition be welded or brazed thereto. Preferably the strips 3 and 4 are otherwise unattached to one'another, so that when bent back and forth they out and extended upward to form a casing 19.about the operating parts 1, 2, 5, 7.

' To complete the inclosure of these parts,

there is also provided (see Fig. 5) a cover 20 of aluminium or other sheet metal having a rim that fits over a lip or flange 21 at the edge of the casing 19. At various points in its circumference this rim is cut and portions 22 bent inward to form locking projections. The lip 21 has notches 23 that allow the projections 22 to pass, and between these notches its thickness is varied in such a way that by turning the cover 20 the rim can be wedged tight beneath them (see Fig. 6). The cover 20 has a fair sized opening and is provided with a mica lining 24; thus there is formed a window for the convenient inspection of the operating parts.

In Fig. 7 I have illustrated an especially advantageous use of my invention in connection with a motor,a three phase alternating current motor, for example. As here shown the motor 30 has ordinary safety fuses 31 and cut-outs 32 like that shown in Fig. l in two of its leads. The fuses 31 can safely be relied on against shortcircuits or extremely heavy overloads; but it is often possible for the motor to be subjected to currents which are not excessive enough to blow the fuses 31, yet which if long enough continued will injure or even destroy the motors insulation by prolonged ticular, when one fuse 31 or 32 blows and .the motor 30 continues to run single phase.

In some cases, also, it may be desirable to allow the motor 30 to be subjected to excessive currents for limited periods (as at starting or under special conditions of use), if only it can be insured that no such current shall continue long enough to be injurious. Now it will be apparent that the cut-out of Fig. 1 will always require time for the member 1 to heat up. before the circuit will be opened, the length of time dependingon the currents; and by a'proper design of the heater 7 and the other parts it is possible to make the heating characteristics of the cut-out similar to those of the motor with which it is meant to be used,-with a proper margin of safety, and thus to insure that the cut-out will always act before any damage can be done, no matter how light or how heavy the overload on the motor, and at the same time it is ossible to allow operation of the motor to e continued for a reasonable time under any overload it can bear at all.

What I claim as new and desire to secure by Letters Patent of the United States, 1s:-

1. An electric cut-out comprising an insulating support having a socket, a pair of terminals associated with said support, a relatively rigid contact member in said socket and means detachably securing it therein accessible at one side of the support, said member being in electrical connection with one of said terminals, a spring contact member secured to said support and in electrical connection with the other of said terminals, fusible means holding said spring contact member flexed toward said rigid member and serving to keep said members in electrical connection with one another, and heater means for releasing said spring contact member electrically connected between said terminals.

2; In an electric cut-out, the combination of an insulatin base having screw shell and center termina s, a spring contact member mechanically secured and electrically connected to said screw shell at one end and extending upward through an opening in said base, another contact member detachably secured to said base, and heater means carried by said detachable contact member and electrically connected between the same and said center contact.

3. In an electric cut-out, the combination of a base comprising insulating parts, center contact means serving to secure said parts together, and a screw shell having a portion clamped between said parts, a spring contact member having one end clamped between said portion of said screw shell and one of said insulating parts, and another contact member secured to said base, and a heater coil connecting said latter contact with the center contact.

4. A fuse member for an electric cut-out consisting of a metal yoke with a metal bar secured across its opening by readily fusible metal.

5. A fuse member for an electric cut-out consisting of a U-shaped metal yoke and a metal bar secured against the ends of the U by readily fusilble solder.

In witness whereof, I have hereunto set my hand this 30th day of April, 1915.

GILBERT WRIGHT. 

